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Stromboli erupting from Craters 1 and 3, 12 June 1996
Activity of Stromboli since 1996
1996-1997
1996
was a particular period in the recent history of Stromboli (and its
residents and visitors). More than ever before, the difficult "relationship"
between this volcano and man has demonstrated its complexity, and both
tourists and people living from tourism had to face that Stromboli is
not a "toy volcano", but that it is potentially dangerous instead.
Activity of Stromboli during the first three months of 1996 generally
was similar to that in previous years. Normal explosive Strombolian
activity of varying intensity was interrupted once, on the evening of
16 February, by a powerful phreatomagmatic (?) explosion. The event
occurred without any evident forerunners, in a manner very similar to
events in March
1989, February
1993 and October 1993 and on 5
March 1995. Intense seismicity (see the plot created by Roberto Carniel, Udine University) lasted
12 minutes; residents in Stromboli village saw the ejection of incandescent
pyroclastics above the summit. This episode was followed by a sudden
drop in seismic activity. A few days later, volcanologists from the
Istituto Internazionale di Vulcanologia in Catania visited the summit
area and found fresh black bombs and Pele's Hair together with blocks
of old, altered material to the north of Crater 1, the possible source
of the explosion. Further, they observed very weak Strombolian activity.
The explosion seems to have been very similar to the previous events
in that it occurred quite suddenly (and therefore had a high danger potential to any people staying
in the summit area) and that it occurred during the winter season (most
recent explosions of that kind have occurred either during autumn or
in February-March). The causes for such explosions and their apparent
clustering in certain periods of the year may be interactions of magma
with water in the uppermost parts of the mountain, maybe after rainy
periods. However, any such relationships would still have to be established
and corroborated before taken for valid. In any case, the 16 February
1996 event once more points to the fact that Stromboli can be indeed
pose significant danger to visitors of its summit area.
After the 16 February explosion, the seismicity of Stromboli declined
dramatically but later gradually increased back to normal values (see
the 1996 seismicity graph prepared by Roberto Carniel, Udine).
After late February, and through mid-April, the seismicity indicated
ongoing normal Strombolian activity with some fluctuations, on levels
similar to late 1995.
A notable increase in the number of seismically recorded eruptive events
occurred on 16 April (1996 seismicity graph) and was soon confirmed by visual
observations, some of them made by Jürg Alean and Roberto Carniel of
Stromboli On-Line. The activity was apparently very similar to that
of July-October 1994, with tall lava fountains and periods of continuous
lava fountaining and spattering. However, this time it appears to have
been largely restricted to Crater 1 while in 1994 there was also very
intense activity from Crater 3. Photos of this activity have been made
available at Stromboli On-Line. There are also a few morphological changes
evident. The remainder of the central cone in Crater 1 (partially destroyed
by the 5 March 1995 explosion) has completely vanished (see the view of Crater 1 from the summit, taken by Juerg Alean
on 28 April 1996), but there is a new, broad feature growing in the
same area, below Pizzo sopra la Fossa. The latter shot also shows that
parts of the "Gemelli" (twins) cones, formed during the summer 1994
activity, are still remaining, and the more southerly one has a vigorously
glowing vent and was the site of occasional eruptions.
Similar activity, with some minor fluctuations, but generally on a very
high level, continued through late May. On the late evening of 1 June
(at 2350 h), a sudden explosion occurred from Crater 1, surprising a
group of mostly German visitors in the summit area (see eyewitness
reports at Stromboli On-line). Four of them were slightly injured.
Two persons initially reported missing were later found unharmed. A
bush fire caused by the fall of hot pyroclastics on the upper slopes
was under control a few hours after the explosions. Stromboli On-Line has a spectacular photo taken (by Wolfgang
Müller) immediately after the event. According to the Istituto Internazionale
di Vulcanologia of Catania (now replaced by the Catania section of the
Istituto Nazionale di Geofisica e Vulcanologia), another, smaller explosion
occurred from Crater 1 on 6 June, this time with less spectacular effects.
Info regarding the activity of Stromboli
on 9-12 June 1996 comes from Marco Fulle (Astronomical Observatory
of Trieste) which is reproduced here in full length. Note that the plot of 1996 seismicity shows fluctuating but very vigrous
eruptive activity through late June 1996.
Photos taken by Marco Fulle on 9-12 June
1996 show that activity was concentrated on two vents, 1/2 and 3/2,
with no eruptions occurring from other vents. While no major morphologic
changes (since April 1995) are evident in Craters 2 and 3, the two large
explosions of 1 and 6 June 1996 have significantly modified Crater 1.
Of the three largest cones formed in the summer of 1994, only part of
the southern "Twin" cone remains. No new cones appear to have formed,
but the crater floor of Crater 1 seems elevated. Accumulation of pyroclastics
on the Sciara side of the crater has led to notable growth of the northwestern
crater rim since the mid-1980's.
Vigorous activity continued through late August, and included a brief
episode of lava effusion from vent 3/1 into the depression of Crater
3 on 16-17 August. Just a few days after that event, a tourist was injured
on his head by a falling bomb while sleeping only about 80 m from the
rim of Crater 3. Appartently, the tourist group to which the unfortunate
man was belonging had been guided to the summit by a guide from Roma
who had chosen the site for sleeping. While many sources reported that
he died as a consequence of his injuries, it is confirmed that he survived
after surgery.
During the
last days of August, the eruptive activity of Stromboli declined abruptly.
Another look on the plot of 1996 seismicity of Stromboli On-Line shows a dramatic
decrease in the number of seismically recorded events. While activity
was still at very low levels, a powerful explosion occurred without
any warning at 1345 GMT (1545 local summer time) on 4 September, launching
incandescent tephra towards the northern side of the summit area. The
source of the explosion may have been Crater 1 although no details are
available up to now. Tourists staying at the crater lookout on the upper
N flank were caught in a shower of tephra, and six or seven of them
were injured. The fall of incandescent tephra onto the outer slopes
of the volcano caused bushfires in some places (see photo below), but
these fires were extinguished soon after. Access to the volcano was
closed by the mayor of the town of Lipari (of which Stromboli is a part)
on the following day, after a recommendation by the provincial authorities
of Messina. Volcanologists of the Istituto Internazionale di Vulcanologia,
Catania, had previously declared that the volcanic activity did not
present any danger to the inhabitants of the island.
Stromboli
was active when my wife and I passed the island while travelling on
the ferry ship from Lipari to Napoli on the evening of 10 October. While
approaching the island from south, two lava fountains shot up from Crater
3 during a 5 minute interval, reaching 80-100 m above the vent (to the
height of Pizzo sopra la Fossa). Each fountain lasted about 20 seconds.
About 10 minutes after the second fountain, an eruption apparently occurred
at Crater 1 (or Crater 2, but this is unlikely). When travelling north
after stopping at Stromboli village, a faint red glow could be seen
once but clouds had begun to cover the summit, and no details were visible.
Roberto Carniel
reports the lowest levels of activity recorded in a long time on 25
October with only 27 recorded seismic events, and a 7-hour period without
seismically recorded eruption. Overall, the seismic
graph shows that Stromboli's activity was at very low levels during
all of October. The levels of activity remained relatively low throughout
1997 but increased somewhat towards the end of the year.
1998
Stromboli produced three larger-than-normal explosions during 1998, one during the winter (on 16 January) and two during the tourist season, on 23 August and on 8 September. The first of these events did not harm anybody, but the later two caused much apprehension among the local population and tourists, and incandescent pyroclastics caused local bush fires. Several further strong explosions occurred towards the end of the year. More detail with photos is available at Stromboli On-line (January event, August event, September event, November event, December event) .
1999
A pair
of strong explosions was reported on 8 (or 9?) April, but no direct
observations of these events were possible due to cloud cover (Stromboli
On-line). Shortly after midnight on 26 August, Stromboli again surprised
tourists who were in the summit area with a powerful explosion that
launched incandescent pyroclastics onto the Pizzo sopra la Fossa. It
appears that there were several people injured, most - as usual - because
they started running away in an unfamiliar and chaotic terrain and fell.
Minor bushfires on the high slopes of the volcano were reported. As
usual, Stromboli On-line
has the details (see also an eyewitness
report at the same site).
I was on the
summit of Stromboli on 15 September and found numerous scoriaceous bombs
on and around the Pizzo sopra la Fossa that had flattened upon impact;
many had diameters of 20 cm or more. In one case, a bomb had fallen
on the rim of one of the primitive shelters made by tourists in the
summit area, and remains of what may have been a sleeping bag were found.
That day, the eruptive activity was at relatively low levels, and I
was able to look inside Crater 3 for a period of about 10 minutes. The
situation was very similar to that observed in August 1991: the floor
of the crater was covered with debris - a mixture of previously ejected
scoriae and partially altered blocks that had fallen off the crater
walls. Explosions pierced this mixture in at least two locations, and
incandescent scoriae sprayed 15-20 m above the crater floor, which lay
about 30 m below the observation point on the S crater rim. During three
hours of observation explosions occurred from up to three vents in Craters
1 and 3, and a persistent, though fluctuating glow was visible after
nightfall in the northermost part of Crater 1. This glow had been visible
already in August, when I passed Stromboli island twice on the ferry
ship connecting the Aeolian Islands with Naples.
On 29 August,
when the ferry ship passed south of the island during the early morning,
a violent thunderstorm raged in the area, and a dense cloud capped the
summit of the volcano. It was amazing to see a chain of tiny flickering
lights slowly moving down the SE flank, and many tourists on the ferry
believed they saw a lava flow - but the lights were actually flashlights
carried by a large group of tourists who had been surprised by the bad
weather and who were struggling to find the path back to the village
at the base of the volcano. As a matter of fact, the thunderstorm had
been forecast days before, and an area of bad weather had been advancing
southwards over Italy. In the same period one man was killed being stricken
by lightning on a cone on Etna, at less than 2000 m elevation.
The third stronger-than-usual explosion of 1999 occurred on 10 October;
fortunately there were few tourists on the summit and no one was injured
(Stromboli
On-line).
2000
Stromboli produced one strong explosion during that year, on 6 September. This occurred during a period of generally low activity and showed that such events may occur at Stromboli at any time, no matter whether the volcano is in a state of elevated or low activity (Stromboli On-line). Two months later a German man who suffered from a grave form of diabetes committed suicide by jumping into one of the active craters (see newspaper article at Stromboli On-line).
2001
The most serious
accident on Stromboli in the past 15 years occurred on 20 October 2001,
when the volcano launched another of its "stronger-than-normal"
explosions. The explosion occurred at about 0235 h and seems to have originated
at the crater formerly named "Crater 2" (now more commonly named
"central crater"). Incandescent bombs fell all over the summit
area and onto the upper slopes of the volcano, causing small bush fires.
A tourist party staying on the Pizzo sopra la Fossa was surprised by the
rain of pyroclastics, and a 41 years-old (other sources say she was 52
years old) woman from Munich (Germany), named Beatrice Steffin, was seriously
injured on the back of her head and fell in coma. A rescue helicopter
brought her to a hospital in Messina where she died of her injuries two
days later. Her family permitted that her (still fully functional) organs
were made available for donation.
Mrs. Steffin was the first person to be killed by eruptive activity
at Stromboli since 1986, when a Spanish
biologist was killed while venturing near the active craters. Most
accidents on this volcano occur due to people losing track on the volcano
in darkness or fog; several people have lost their lives that way in
recent years.
More information on the 20 October 2001 accident can be found at Stromboli
On-line (go also here
for further information, including a seismic graph).
2002
2002
marks a significant change in the recent eruptive dynamics of Stromboli,
although this occurred only at the very end of the year. Before the
major eruption that started on 28 December 2002 (and is continuing as
of mid-January 2003), the volcano behaved much in the same manner as
during the previous years. Two powerful explosions occurred during the
year, on 23
January and 24
July. I had the privilege to witness the latter of these from the
harbor of Stromboli island, only eight hours after having been at the
summit together with a group of French excursionists and local mountain
guides. Later visits to the summit of the volcano revealed that several
large lithic blocks had fallen beyond the usual observation point (the
"Pizzo"), along the descent route on the southeastern "back
side" of the volcano. Juvenile ash fell in minor quantities in
the harbor area and onto boats anchoring nearby. The explosion occurred
during a period when the "normal" persistent activity of the
volcano showed a gradual increase from very low levels experienced during
the spring of 2002.
Throughout the summer and autumn of 2002, Stromboli became more and
more vigorously active. In late October, at the time when Mt. Etna began
a major flank eruption, eruptive activity occurred from all three craters,
which contained a total of six active vents. High levels of activity
continued in November and December, and on several occasions there were
rumors of a lava flow descending the Sciara del Fuoco. As a matter of
fact these were unfounded, but nonetheless prophetic, because on 28
December Stromboli did produce its first major effusive eruption since
1985-1986.
The 2002-2003 eruption
At
the end of 2002, Stromboli showed its violent face in an unprecedented
manner, with a multifaceted eruption that lead to the total evacuation
of the island and aroused fears of a catastrophic collapse event at
the Sciara del Fuoco. A first lava flow occurred on 28 December and
was peculiar for the velocity at which it descended to the sea. Renewed
lava effusion on 30 December was accompanied by a significant collapse
on the unstable scree of the Sciara on 30 December, causing a tsunami
(sea wave triggered by seismicity or entrance of collapsing debris into
the sea), which damaged structures on the shores of the island. Several
persons were injured, but fortunately there were very few tourists on
the island at that time, otherwise there would have been probably much
more serious consequences.
More detailed information with spectacular photographs is available
on the following web sites: INGV-Catania,
Stromboli On-line (report
and photo
pages), and Decadevolcano.com.
What should be added here is that the Sciara del Fuoco landslides dislodged
an estimated 50 million cubic meters of rock (only one-fifth of these
above the sea level), and access to the island remained largely closed
until the spring of 2003, with only residents being permitted to stay
there, although they were rather recommended to keep away. In late February,
all residents returned to the island. There was virtually no tourism
on the island for the first months of 2003, dropping tourism business
on the Aeolian Islands into a deep crisis, from which it recovered gradually
over the summer of 2003, when access to Stromboli island was again permitted.
The eruption of lava from a new vent cluster below the northeastern
crater of Stromboli continued at a somewhat lower, and fluctuating,
effusion rate through the first months of 2003, and lava did no longer
reach the ocean. In the spring of 2003, sporadic ejections of spatter
from the effusive vents led to the growth of a cluster of steep-sided
hornitos, which unfortunately were not visible to the visitors that
were allowed to climb to 400 m altitude from mid-April onward, and virtually
no photographs of them have been posted anywhere on the web. I had the
luck to see these things once during a helicopter overflight (after
the end of the effusive eruption), through a gap in the clouds, and
therefore did not succeed in obtaining a good photograph of them.
The extended period of lava emission was interrupted, on 5 April
2003, by one of the most powerful explosions ever seen at the
summit craters of Stromboli. It was great luck that this explosion occurred
in a period when access to the volcano was prohibited and there were
few visitors on the island. A group of volcanologists and mountain guides
making a routine helicopter overflight at the time of the explosion
barely escaped the rapidly expanding eruption column; after that experience
one of the mountain guides vowed to never enter a helicopter again in
his life. Small pyroclastic flows were generated, which descended the
Sciara del Fuoco, and the summit area ("Pizzo"), formerly
a popular tourist lookout, was covered with up to 20 cm of fresh pyroclastics.
All monitoring equipment located in this area, including the INGV monitoring
camera, was destroyed. The explosion occurred with virtually no warning,
as all major explosions at Stromboli in the past years. Had it occurred
in August 2002, it would have caused hundreds of deaths, for at that
time the summit was visited by hundreds of tourists at a time, with
still dozens more climbing or descending at the same time.
Effusive activity, accompanied by frequent rockfalls on the Sciara del
Fuoco, continued until 22 July 2003, making this one of the longest
periods of continuous lava effusion during the past 100 years at Stromboli.
During the last weeks of lava outflow, a gradual resumption of Strombolian
activity at the summit craters was observed, which led to the return
of more "normal" conditions. Since 22 July, the volcano displays
its normal Strombolian activity, but visitors are allowed to climb no
higher than 400 m (for the last 110 m it is obligatory to be accompanied
by an authorized mountain guide). A few visitors do go higher sometimes,
but any trespassing is strictly prohibited, and punished with a fee
of 250 Euro and possible legal consequences.
Copyright © Boris Behncke, "Italy's Volcanoes: The Cradle of Volcanology"